TxDOT’s Waco District in the heart of Texas continues to strive for excellence, taking their efforts to the next level by engineering and matching products, increasing competition through suppliers and contractors. 

The Texas Department of Transportation (TxDOT) understands the true value of protecting their investment with virtually half of their available funding dedicated to pavement preservation and ongoing roadway maintenance.

With the current fiscal condition of most public agencies, maintaining pavements that are in “acceptable or above acceptable” condition is paramount given the cost of rehabilitation or reconstruction. It costs approximately $.20 on the dollar to maintain “acceptable” or “above acceptable” conditions of pavements using conventional chip seals. 

TxDOT Districts go to contract with district-wide chip seal contracts in the Fall/Winter timeframe to be constructed the following Summer. This allows aggregate suppliers time to produce and deliver the aggregate prior to when the contractor’s working days commence. It also allows the agency the time to do all necessary due diligence and preparation work on roadways slated for an upcoming chip seal. 

The Waco District let their project on October 21, 2010, with an engineer’s estimate of slightly over $12M. The District allowed 60 working days on the project for 347 centerline miles. Brannan Paving Company of Victoria, TX, was the winning bidder on the project, coming in less than 1% over the estimate. The project included a variety of engineered options such as TxDOT Grade 3 (5/8” top size aggregate) matched with the typical emulsions options such as CRS-2, CRS-2P and CHFRS-2P for use on rural, less traveled roadways and TxDOT Grade 4 (1/2”top size aggregate) in more populated rural sections. In addition, Brannan Paving Company also used pre-coated Grades 3 and 4 matched with high performance asphalt options such as AC 20-5TR and AC 15-P, AC-20XP and AC 10-2TR for use on roads with higher speed limits, as well as increased traffic volume facilities. These products, when matched-up as they are, provide the contractor the assurance that they can maximize daily production with minimal delays and driver complaints with confidence. All of this – combined with the ability to choose the most effectively priced materials for the application – made this project a success, not only at bid time, but for years to come; a well-suited pavement estimated to last 5 to 7 years or longer. 

To understand the complexity of the project, the asphalt component of a chip seal is where the majority of the project cost resides. In this particular case, there were 2.569 million gallons of asphalt, at an average price of $2.71 per gallon, for an approximate total of $7M, or 57% of the Engineer’s estimate. There are three suppliers: Martin Asphalt (AC 20-5TR), Ergon Asphalt and Emulsions (CRS-2 and CRS-2P) and Valero Asphalt (AC-15P). 
The aggregate component was bid as a contractor option for crushed stone, both pre-coated and uncoated in Grades 3, 4 and 5 pitted against TXI Lightweight Expanded Shale Aggregate in the same types and grades. There were 55,888 cubic yards, at an average Engineer’s estimate of $47 per cubic yard, for a total investment of $2.62 million or 22% of the estimate. 

In Texas, both lightweight aggregate (TxDOT Item 302-Type L or PL) and crushed stone (TxDOT Item 302-Type B or PB) are tested on an equal scale and therefore have to meet identical quality requirements. Taking it one step further, TxDOT has their own quality catalog, where all TxDOT-quality monitored bituminous aggregate sources used in Texas are rated on a surface aggregate classification system, commonly referred to as the SAC rating. An up-to-date version of this catalog is available online here. 

The SAC rating of TXI Lightweight Expanded Shale Aggregate in all TxDOT types and grades is SAC A. The majority of the available crushed stone sources in Texas are SAC B. This means with regard to durability and wet weather accident prevention statistics, the lightweight aggregate is superior. 

Brian Lindsey, Senior Project Manager, Brannan Paving, had the flexibility to choose which aggregate and asphalt source to use on each roadway. Price, availability, performance and customer service were all key factors in the process. While Mr. Lindsey’s other aggregate choices were much closer to the project(s), thus freight playing a significant role in the delivered price, he selected TXI Lightweight Expanded Shale Aggregate for over 65% of the project.

TXI Lightweight Expanded Shale Aggregate remains a cost-effective, high-performance aggregate that is used extensively in Texas chip seal projects all over the Central and Eastern Regions of the state. Allowing the contractor the option to choose suppliers and materials that were measured on a heavily monitored/level playing field resulted in the most cost-effective way to meet all goals.